What size tracheal tube?
	Date: Sun, 21 Jul 1996 07:12:34 From: Greg Winterflood [gnwflood@OZEMAIL.COM.AU] Having just visited the Website of Trauma.Org at Moulage and failed their moulage practice by choosing the wrong sized ETT I wish to ask the collective wisdom of the list this question: What is the correct sized endotracheal tube for trauma resuscitation in an adult? I opt for a 7.0mm ID Mallinckrodt be the patient male or female. My reasoning is that I'm going to get a 7 in more often on the first go. Also, I don't need to waste time making a decision about tube size as that has been decided before the patient hits the deck. I am considering having a 7 as the only tube size on the adult resuscitation intubation tray. "Tube" would then simply mean "Pass me the only one available". Doing this is based on a principle which I have heard was adopted by the British Army in the Falklands conflict. Apparently, they had only one type of crystalloid for iv administration. No decision to be made. A request for fluids was met with a bag of saline, not with the question "What do you want: Hartmanns, Dextrose, Saline?" Modern tubes have high volume low pressure cuffs and "one size fits all" - think about the 5.5mm microlaryngoscopy tube. This is different from the old days of red rubber tubes when cuff size and cuff pressure were related to the size of the tube and choosing a big tube for a big trachea was important. Any thoughts?
	Date: Sat, 20 Jul 1996 22:12:06 From: Harold C. Cohen [hcohen@WALDENU.EDU] My rule of thumb for adult ET size (excluding evidence of airway swelling) is Male- 8.0 and Female- 7.5. At least academically, in many adults, a 7.0 tube may require you to overinflate the balloon and either cause tracheal stenosis. Then again, an ED physician mentor of mine always said that "the 7.0 you get is better than the 8.0 you miss.
	Date: Sat, 20 Jul 1996 18:46:38 From: Don Elton [delton@PRO-CAROLINA.CTS.COM] I'd prefer using an 8.0 or at least 7.5 ETT whenever possible as it will allow you to have a bronchoscopy via the ETT later if needed.
	Date: Sat, 20 Jul 1996 18:38:56 From: Harvey Louzon [harvey@MCS.NET] One can always intubate with a cuffed ETT that is too small and a laryngyscope blade that is too large but the opposite is not true. This is the rationale for using a cuffed tube that is slightly small. Since I often perform BNTI I, certainly, am not going to be the one to criticise the use of a 7.0 or 7.5 mm tube since that is the largest tube that one can generally pass through the nose. When I perform OTI, however, I generally use a larger tube. In the ED our main concern is simply getting that tube in. If a smaller tube makes that easier than by all means use it. If a larger tube is needed to accommodate a bronchoscope then let them exchange it using the 'Seldinger' technique in the ICU under more controlled conditions after the patient is stabilized and well oxygenated. We did have a discussion about this a while ago and someone raised the issue of increased airway resistance in patients (say with reactive airway disease) who are intubated with a small tube. I expressed the opinion at that time that the main source of resistance was in the small airways and not at the level of the tube but I have since seen a study that simulated respiratory mechanics and found a considerably higher work of breathing with smaller tubes (although this was a peds study and the percentage change in tube size from, say, a 4.0 to a 4.5 is larger than in adult 7.0 - 8.0 tubes). Whether this would delay weaning from mechanical ventilation or not I do not know, but would make the same observations that I did above concerning the problem of small tube sizes on the ability to perform bronchoscopy, i.e., if it crimps your style then exchange it in the ICU. Nevertheless, I am interested in the theoretical problem of small tube sizes in worsening airway resistance and if anyone has any experimental data I would like to see it.
	Date: Sun, 21 Jul 1996 00:49:02 From: Don Elton [delton@PRO-CAROLINA.CTS.COM] I agree that if there's any doubt at getting a tube in during an emergency airway problem and if a doctor/therapist/paramedic feels that in his hands a smaller tube will be more likely to be properly placed then this is the way to go in an emergency. All things being equal though I'd rather see the larger tube for better suctioning, possible later bronchoscopy, and airway resistance. Artificial airway resistance, incidentally, is really not a factor in patients with high intrinsic airway resistance or at least is a minor factor. There are, in my way of thinking, two types of airway resistance to be concerned with... One for laminar flow where pressure required is going to be related to flow in a linear or nearly linear way where doubling flow will required double pressure. The second is turbulent flow where no amount of pressure increase will result in any real increase in flow. Patients with very high airway resistance tend to be in this latter category and their flow-maximum is set somewhere in their own airways and this flow maximum isn't influenced much by an ET tube. Patients with lower resistances though can see an increase in their effective airway resistance though since resistances in series are additive and small increases above the normal low airway resistance seen in adults can result in large percentage changes to the amount of pressure needed to drive a given flow. While these resistances are still additive in patients with high resistance, the percentage increase isn't as great and probably not nearly as important to the patient.
	Date: Sun, 21 Jul 1996 23:01:28 From: Antony Nocera [tonynoce@OZEMAIL.COM.AU] For oral intubation I routinely use 9.0 ETT for males & 8.0 ETT for females; however I will always have the next size down on the intubation tray ready in case it is needed (which is rare). For nasal intubation I will go 8.0 ETT in males & 7.0 ETT in females & again I will have the next size down on the intubation tray ready in case it is needed. The potential problems with small tubes & using higher cuff volumes in big tracheas are: 1) The ETT may rotate around the cuff & bring the bevel to lie parallel to or against the wall of the trachea. This may make it difficult to advance suction catheter along the ETT or produce an obstruction to the ETT. 2) A distended cuff could herniate down over the bevel & produce an ETT obstruction 3) The cuff pressure in a smaller ETT is going to be higher to achieve a seal & plus the area of contact of the cuff against the tracheal wall will be smaller c.f. with a larger tube increasing the risk of a pressure point in the tracheal mucosa. 4) In the Hagen Poiselle formula, laminar flow is proportional to radius to the fourth power, in the Fanning equation for turbulent flow; flow is porportional to radius to the fifth power. Normally airflow in the upper airways is turbulent down to the fourth airway division & laminar beyond that. For the intubated patient using a larger ETT will decreases the work of their breathing when they are breathing through an ETT. 5) If you get caught out with a patient biting down on an ETT the smaller the ETT the greater the obstruction that will be caused in a shorter time frame.